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Remembering and Restoring Expanded Rows in TreeDataGrid for .NET MAUI

Updated on Sep 26, 2025

Environment

Version	Product	Author
11.1.0	Telerik UI for .NET MAUI TreeDataGrid	Dobrinka Yordanova

Description

I want to remember the expanded rows in the TreeDataGrid and restore them later. What is the most efficient way to achieve this?

This knowledge base article also answers the following questions:

How can I store expanded items in TreeDataGrid for later use?
How can I restore the expansion state in TreeDataGrid after changes?
What is the best way to manage expanded rows in TreeDataGrid?

Solution

To achieve the scenario you can use one of the following approaches:

Using Expand and Collapse methods
Using IsExpandableBinding property of the TreeDataGridDescriptor

Using Expand and Collapse Methods

To achieve this, follow these steps:

Use Expand() and Collapse() methods to expand or collapse items.
Use the IsExpanded method to check whether an item is expanded.
Store the expanded items in a collection, such as a List<YourDataClass>.
Iterate through the collection to restore the expanded state by calling the Expand() method.

public partial class MainPage : ContentPage
{
    public MainPage()
    {
        InitializeComponent();
        this.BindingContext = new ViewModel();
    }

    // Collection for storing expanded items
    List<Data> expandedItems = new List<Data>();

    private void Button_Clicked(object sender, EventArgs e)
    {
        var items = (IEnumerable)this.tdg.ItemsSource;
        this.expandedItems = new List<Data>();
        AddExpandedItems(items, expandedItems);
    }

    private void AddExpandedItems(IEnumerable items, List<Data> expandedItems)
    {
        foreach (Data item in items)
        {
            if (this.tdg.IsExpanded(item))
            {
                expandedItems.Add(item);
            }

            IEnumerable childrenOfTheItem = item.Children;
            AddExpandedItems(childrenOfTheItem, expandedItems);
        }
    }

    private void Button2_Clicked(object sender, EventArgs e)
    {
        foreach (Data item in this.expandedItems)
        {
            this.tdg.Expand(item);
        }
    }
}

Using `IsExpandableBinding`

As an alternative, use the IsExpandableBinding property at the descriptor level. This approach provides direct control over the expandability of rows via data binding.

Add a bool property in the data model to indicate whether an item is expandable.
Bind this property to the IsExpandableBinding property of the TreeDataGrid descriptor.
Implement the logic in button clicks to get and restore expanded items.